This invention relates to endoscopes or borescopes of the type in which a miniature video camera is mounted at the end of a flexible elongated insertion tube, and in which illumination is carried on a fiber optic bundle to the distal end of the insertion tube to illuminate a remote target area.
The invention is more particularly concerned with apparatus to extend the range of the borescope or endoscope, that is, devices which increase the separation from the target area to the borescope's video processor unit.
Currently, video borescopes are limited in length to about fifty feet (sixteen meters). This distance represents the maximum effective distance that the fiber optic bundle in the insertion tube can carry illumination for illuminating the target area. As a result, it is sometimes necessary to place the video processor in a precarious or highly inconvenient location just to permit the borescope to reach a desired remote target area, which may be deep within a turbine, boiler, or other complex piece of equipment.
Where a color endoscope or borescope is employed, sequential primary color light is supplied over the fiber optic bundle to illuminate the target area sequentially with red, blue, and green light. This can be generated using a white light source and separated into primary colors with a color filter wheel, whose rotation speed and phase are synchronized with the field rate of the video signal produced by the video camera. A sequential color light wheel device of this type is disclosed in Longacre U.S. Pat. No. 4,523,224. This device is conventionally contained within the video processor unit of the endoscope or borescope system.
An interface module at the proximal end of the borescope insertion tube, or at the proximal end of an umbilical or extension coupled to the insertion tube, removably couples to the video processor unit. This interface module includes electrical connectors to connect the video camera to circuitry in the video processor. The interface module also includes an optical interface that couples the proximal end of the fiber optic bundle to the sequential color light source within the video processor unit. An interface module of this type is disclosed in Danna et al. U.S. Pat. No. 4,539,586.